A conventional display panel using organic electroluminescence (EL) is connected through a flexible substrate (flexible wiring plate) to a print substrate which feeds power supply or signals to the drive circuit of the display panel. For example, Patent Literature 1 discloses formation of an alignment mark having a predetermined shape (such as an elliptical shape) in a flexible wiring plate to prevent positional deviation in the rotational direction when the flexible wiring plate is connected to a display panel.